Multiple tube-rolling pilger mills

ABSTRACT

A pilger mill comprising a pair of sizing rolls, each provided with a plurality of facing parallel tube-rolling grooves, mounted on a reciprocating carriage which, during its reciprocation, drives by means of a rack-and pinion transmission the roll pairs at the unison and in opposite directions. Each roll groove comprises a reducing section and an idle section. The reducing sections of each groove pair are angularly offset with respect to the reducing sections of the other grooves of each roll so that, in operation, the reducing of only one tube at a time is effected. The idle sections of all parallel grooves extend for an angle including an idle angle fraction which is aligned in all grooves. Said idle angle fractions encircle with a certain clearance the tube sections therebetween, thus permitting the forward stroke of the reciprocating carriage. At least one pair of roll grooves comprises, in addition to the reducing sector, a tube-smoothing or finishing sector.

United States Patent Persico [451 Mar. 21, 1972 [54] MULTIPLE TUBE-ROLLING PILGER MILLS [72] Inventor: Giuseppe Persico, 69, Via Pio X, Volpago Del Montello (Treviso), Italy [22] Filed: Sept. 23, 1969 [21] Appl. No.: 860,297

[30] Foreign Application Priority Data Sept. 28, 1968 Italy ..7364 A/68 July 23, 1969 Italy ..7l98 A/69 [52] U.S. CI ..72/189, 72/208, 72/214, 72/221 [51] Int. Cl ..B21b 21/00 [58] Field of Search ..72/214, 221, 364, 189,193, 72/208, 220, 188

[56] References Cited UNlTED STATES PATENTS 3,503,241 3/1970 Vom Dorp et al ..72/214 2,988,937 6/1961 Nowakowski..... ...72/214 2,703,999 3/1955 Gille 72/208 459,765 9/1891 Parmelee 72/198 545,513 9/1895 Mannesmann.

ll TI MI 1,516,153 11/1924 Gorman et al ..72/221 2,085,729 7/1937 Coe ..72/214 3,030,835 4/1962 Krause.... ..72/214 Primary Examiner-Charles W. Lanham Assistant Examiner-Michael J Keenan Attorney-Edwin E. Greigg [5 7] ABSTRACT A pilger mill comprising a pair of sizing rolls, each provided with a plurality of facing parallel tube-rolling grooves, mounted on a reciprocating carriage which, during its reciprocation, drives by means of a rack-and pinion transmission the roll pairs at the unison and in opposite directions. Each roll groove comprises a reducing section and an idle section. The reducing sections of each groove pair are angularly ofiset with respect to the reducing sections of the other grooves of each roll so that, in operation, the reducing of only one tube at a time is effected.

The idle sections of all parallel grooves extend for an angle including an idle angle fraction which is aligned in all grooves. Said idle angle fractions encircle with a certain clearance the tube sections therebetween, thus permitting the forward stroke of the reciprocating carriage.

At least one pair of roll grooves comprises, in addition to the reducing sector, a tube-smoothing or finishing sector.

6 Claims, 16 Drawing Figures PAHENIEH MAR 2 1 I972 SHEET 1 OF 6 E895 D 17 2 9659 DHCJI PATENTED MAR 21 I972 SHEET 3 [IF 6 PATENTEDHARZI I972 SHEEI S UF 6 PATENTEDMARZ] I972 SHEET 8 OF 6 MULTIPLE TUBE-ROLLING PILGER MILLS In order to reduce by rolling the tube diameter, usually in a plurality of subsequent steps or stages, by the so-called pilger mill method, multiple pilger mills are employed which comprise pairs of rolls, provided with a plurality of facing parallel tube-rolling grooves. Said rolls are mounted on a reciprocating carriage, or in a reciprocating housing, which, during its reciprocation, drives, usually by means of a rack-and pinion transmissions, the roll pairs at the unison and in opposite directions. Each roll groove comprises a reducing section and an idle section. When the said idle sections of each groove lie in front of the tube therebetween, this is encircled with a clearance and may be allowed to advance freely during the forward stroke of the carriage, when the said pinions meshing with the racks are rotated back.

By these pilger mills, for each tube-reducing stage, a fulllength rolling mill must be provided and an independent strong motor and/or driving means must be fitted for reducing each tube section at each stage.

This renders necessary a very large floor space for the whole reducing mill and, in addition, the provision of a plurality of very powerful separate driving means, one for each reducing stage or step.

According to a characteristic feature of the invention, a more compact and less floor space requiring multistage rolling mill may be constructed by providing a reciprocating carriage in which a pair of multistage tube-rolling rolls are rotatably mounted, so as to be rotated by suitable driving means in one direction, each roll of the pair being provided with at least two, and preferably three or even more grooves, each comprising an active or positive reducing sector and an idle sector permitting the free passage, with sufficient clearance, of a tube section fed in correspondence therewith.

According to another important characteristic feature of the invention, the reducing sectors of each roll groove pair extend for an angle which is completely angularly offset with respect to the reducing sectors of the other grooves of each roll so that, in operation, the rolling of only one tube section at a time is effected, although the mill is provided for effecting the rolling of more than one tube section.

The idle sections of all parallel grooves, on the contrary, extend for an angle including an idle angle fraction which is aligned in all grooves. Said idle angle fraction of the grooves encircles with a certain clearance, the tube section therebetween, thus permitting also, thanks to the provision of a conventional freewheel mechanism rendering inactive the meshing of the said rack-and pinion transmission, the free advancement of the whole set of said tube sections, which, at the beginning of the next return stroke, may be again clamped and rolled subsequently between each of the corresponding subsequent active roll groove sections.

According to still another characteristic feature of the invention, also, the pair of grooves designed for reducing to the final size the tube section therebetween, are provided with an additional tube-smoothing or finishing section which ends just adjacent to said idle sector.

The invention will be better understood from the following specification of one preferred embodiment of a three-stage tube rolling pilger mill, whose main parts are diagrammatically shown in the accompanying drawings, wherein:

FIG. 1 is a side view of a mill housing including a carriage provided with a pair of three-stage tube-reducing rolls, and the power means for the stepwise feeding of tube sections of different lengths;

FIG. 2 is an enlarged vertical section through the mill carriage, on line IIII of FIG. 1;

FIG. 3 is an approximate diagram showing the different angular extensions of the reducing sectors of three adjoining grooves of each roll of the pair, as well as the common angular extension of the three aligned idle sectors;

FIG. 4 diagrammatically shows for the rolling groove having the smallest transverse diameter, the active or reducing sector and the whole idle sector, which includes also the common idle sector fraction 8 shown in FIG. 3;

FIGS. 5A, 5B, and 5C show three vertical sections through the axes of three tube sections during the feeding stroke of the tubes through the idle sections of the milling grooves;

FIGS. 6A, 6B, and 6C are sections like the preceding ones and in which only the smaller diameter tube is being reduced by rolling in FIG. 6A, while the other tubes are still clear of the corresponding rolling sectors of the grooves;

FIGS. 7A, 7B, and 7C are sections like the preceding ones and show, respectively, the smaller tube section snugly adhering to the last part of the roll groove, acting as tube-smoothing groove part; the intermediate tube section engaged between two reducing roll groove sections and the larger tube section clear of any engagement with the roll grooves; and

FIGS. 8A, 8B, and 8C are sections like the preceding ones and show, respectively, the smaller tube section still engaged in the last part of the smoothing or finishing roll groove; the intermediate tube section in a position clear of the corresponding roll grooves and the largest tube section engaged between the reducing rolling sectors.

With particular reference to FIGS. 1 and 2 of the drawings, 1 is a tube-rolling mill housing in which a carriage 2 is reciprocated by means of a motor-driven crank 3 and connecting rod 4. On the carriage 2 a pair of twin rolls R1 and R2 are rotatably mounted. Each of the twin rolls is provided with three circumferential grooves, viz roll R1 has three spaced parallel grooves G11, G12, and G13 facing like grooves G21,

' G22, G23 milled in the twin roll R2 and defining together, in

correspondence of their oppositely lying surfaces, three revolving sections composed of slightly spaced pairs of arcs of circle and through which the tubes T1, T2, T3, which are the tubes to be reduced and finished by cold rolling, are processed.

In these circular sections, the tubes T1, T2, T3, previously threaded on conventional supporting mandrels M1, M2, M3 are first fed, by sections of predetermined lengths by means of, for example, hydraulic pistons sliding in cylinders HCl, HC2, HC3 and whose piston rods are provided with conventional clamping jaws J1, J2, J3 and then the advanced lengths are reduced and/or finished by being rolled back, according to the so-called pilgrims mill process, by the rolling sections of the three superposed pairs of twin grooves when the carriage 2 is driven back by the crank and rod system 3-4.

During this driving back, the pinions P1, P2 at the ends of the trunnions of rolls R1, R2, FIG. 2, are rotated by meshing with fixed racks PR1 PR2.

In order to avoid that the three tube sections T1, T2, T3 be reduced at the same time, which would require an excessive power output, the reducing sections of each roll pairs are circumferentially and angularly offset as shown by way of example in FIG. 3, wherein a, )3, and 'y indicate the approximate (decreasing) amplitude of the angles along which the three adjoining rolling sectors extend in the grooves G11-G2l, Gl2-G22, and G13G23, while the angle 8 is the angle corresponding to the idle sections of all three pair of grooves, said idle sections encircling all three tube sections at the same time during the forward strokes of the carriage 2.

The operation of the just-described arrangement is apparent by examining the working cycle shown in FIGS. 5A through 8C of the drawings:

In the roll position shown in FIGS. 5A, 5B, and 5C the feeding stroke of the tubes T1, T2, and T3 has just been completed and the groove pair G1 1-G21 is at the starting of the rolling of the most reduced section T1 of the tube, while the other tube sections T2 and T3 are clear of the corresponding roll grooves G12-G22 and G13-G23.

By continuing the rotation of the rolls R1 and R2 in opposite directions (see arrows) as shown in FIGS. 6A to 6C, due to the shifting of the carriage 2 and the consequent driving of the roll pinions on the racks PR1 and PR2 (FIG. 1), the section of the tube Tl which is clamped between the rolling sectors of grooves G11 and G21 is completely rolled to its final size, while the other tube sections T2 and T3 are not rolled, as they are still clear of the corresponding rolling sections of grooves G12-G22 and 613-023.

By further continuing the rotation of the rolls R1 and R2, by arriving to the angular position as shown in FIGS. 7A to 7C, the just-rolled section of the tube T1 is outside of the reducing sectors of grooves 01 1-021 but is in contact with the tail end of these grooves, where it is subjected to a smoothing or finishing while the intermediate-size tube section T2 is clamped between and rolled by the reducing sectors of grooves 012-022 and the tube section T3 is still clear of the reducing sections of grooves 013-023.

By still further continuing the rotation of rolls R1 and R2, by arriving at the angular position as shown in FIGS. 8A to 8C it may be seen that the smallest rolled tube section T1 is still in contact with the last part of the tail end of the grooves 011-021 beyond the reducing section thereof; the rolled intermediate tube section T2 is beyond the reducing sectors of grooves 012-022 and clear of these grooves, while the largest tube section T3 is being reduced in groove sections 013-023.

From the foregoing it is apparent that a multistage tubereducing pilger mill has been devised which while occupying a restricted space and employing a normal power, for effecting a substantial reduction and finishing of tubes in a plurality of subsequent steps by means of the same roll pair, presents the same advantages and an increased output as the tubereducing multistage pilger of known type.

Of course the invention may undergo some changes, without departing from the spirit thereof or the scope of the appended claims.

Thus the active diameter and numbers of grooves in each roll pair and the angular extension of the reducing sectors may vary, and also the driving arrangements of the carriage may vary and the systems for feeding the tube sections to be rolled.

Thus the present invention provides a cold rolling multiple pilger mill with a set of three rolling sections, and with means for feeding therebetween in a differentiated manner the tubes to be sized proportionally to the lengths of the tubes same. A characteristic feature of the milling system of the invention is that the tube being the smallest in diameter is the first to be reduced in the working stroke of the sizing rollers, whereby a long groove section can be provided for the smoothing and finishing of the outer surface of said tube both in the working and in the idle stroke of said rollers, without any change in the ratio between the diameter and the working stroke of the machine, no substantial increase in the thrusts to the stand being therefore involved.

Many changes and modifications will be apparent to those skilled in the art without departing from the scope of the invention as set forth in the appended claims.

I claim:

1. A multiple tube-rolling pilger mill, comprising:

a. a reciprocating rolling carriage,

b. a pair of cooperating sizing rolls rotatably mounted in said carriage,

c. means for rotating the said rolls during the reciprocating movement of said carriage,

d. a plurality of circumferential parallel tube-rolling grooves on each of said rolls, each of said grooves on one roll having a complementary groove on the other roll,

e. each roll groove comprising a tube reducing section and an idle section,

f. the tube reducing section of one of said parallel tube rolling grooves and also the tube reducing section of its complementary groove being circumferentially and angularly offset from the tube reducing section of another parallel tube rolling groove and also the tube reducing section of its complementary groove,

g. the idle sections of each of said parallel grooves extending for an angle including an idle angle fraction which is aligned in all grooves, and

h. means for advancing the tubes being rolled at the end of each stroke of the carriage.

2. A multiple tube-rolling pilger mill, according to claim 1,

wherein the parallel grooves on each roll are of different diameter in transverse section and have reducing sections of different lengths.

3. A multiple tube-rolling pilger mill according to claim 1,

wherein the grooves are three, of decreasing diameter in transverse section and the corresponding reducing sections are of increasing lengths, and form together an angle of less than 360", the groove parts outside said reducing sections being aligned in angular position on each roll and each having a portion which permits simultaneous axial shifting of said tubes through the twin groove sections of the rolls when said portions are adjacent the tubes.

4. A multiple tube-rolling pilger mill according to claim 1, wherein the grooved rolling rolls are mounted in a carriage provided with means for reciprocating same in a housing; said rolls being provided at their ends with pinions effecting the positive driving of the rolls.

5. A multiple tube-rolling pilger mill according to claim 3, wherein the reducing sections of the grooves of said rollers are so offset with respect to one another that in the same working stroke of the stand first the tube which is smallest in diameter, then the intermediate diameter tube, and finally the one having the larger diameter are rolled in succession, the grooves for the smallest diameter tube being provided with an extended portion for smoothing and finishing the outer surface of said last-named tube, while the other tubes are being reduced.

6. A multiple tube-rolling pilger mill according to claim 2, comprising means for advancing a plurality of different tube lengths through said pair of rolls at the beginning of each tube reducing operation. 

1. A multiple tube-rolling pilger mill, comprising: a. a reciprocating rolling carriage, b. a pair of cooperating sizing rolls rotatably mounted in said carriage, c. means for rotating the said rolls during the reciprocating movement of said carriage, d. a plurality of circumferential parallel tube-rolling grooves on each of said rolls, each of said grooves on one roll having a complementary groove on the other roll, e. each roll groove comprising a tube reducing section and an idle section, f. the tube reducing section of one of said parallel tube rolling grooves and also the tube reducing section of its complementary groove being circumferentially and angularly offset from the tube reducing section of another parallel tube rolling groove and also the tube reducing section of its complementary groove, g. the idle sections of each of said parallel grooves extending for an angle including an idle angle fraction which is aligned in all grooves, and h. means for advancing the tubes being rolled at the end of each stroke of the carriage.
 2. A multiple tube-rolling pilger mill, according to claim 1, wherein the parallel grooves on each roll are of different diameter in transverse section and have reducing sections of different lengths.
 3. A multiple tube-rolling pilger mill according to claim 1, wherein the grooves are three, of decreasing diameter in transverse section and the corresponding reducing sections are of increasing lengths, and form together an angle of less than 360*, the groove parts outside said reducing sections being aligned in angular position on each roll and each having a portion which permits simultaneous axial shifting of said tubes through the twin groove sections of the rolls when said portions are adjacent the tubes.
 4. A multiple tube-rolling pilger mill according to claim 1, wherein the grooved rolling rolls are mounted in a carriage provided with means for reciprocating same in a housing; said rolls being provided at their ends with pinions effecting the positive driving of the rolls.
 5. A multiple tube-rolling pilger mill according to claim 3, wherein the reducing sections of the grooves of said rollers are so offset with respect to one another that in the same working stroke of the stand first the tube which is smallest in diameter, then the intermediate diameter tube, and finally the one having the larger diameter are rolled in succession, the grooves for the smallest diameter tube being provided with an extended portion for smoothing and finishing the outer surface of said last-named tube, while the other tubes are being reduced.
 6. A multiple tube-rolling pilger mill according to claim 2, comprising means for advancing a plurality of different tube lengths through said pair of rolls at the beginning of each tUbe reducing operation. 